This is a really interesting question but not one that has been addressed yet. In part because the use of the internet for socializing is fairly recent (IE in the last decade or two) and measuring the effects on long-term isolation in humans requires...decades of research. Using animal models would be faster but as far as I am aware we have no animal models of online social networks.

What we do know is that the use of the internet for socializing affects our loneliness and quality of life. This research is still fairly new since social media is fairly new and involves very quickly. Our current understanding is that socializing online enhances relationships and quality of life but cannot replace in-person connections. A study in Israel found that using the internet increased people's quality of life if they saw their family regularly (a proxy measurement of in-person interaction) but had no affect on those who did not.

Additionally, the way internet use affects us is often different depending on your age. For adolescents, the more time spent online was correlated with higher loneliness while in older adults the opposite was true. This may be do to the differences in how people from different age groups use the internet: older adults tend to go online more often to communicate compared with adolescents.

It's hard to make any concrete statements at this point since we just don't have the data yet. From the information we do have, I think it's reasonable to hypothesize that using the internet to socialize can help reduce the negative affects of isolation but are not a good replacement for offline relationships.

Loneliness and social media (Israeli study): https://journals.sagepub.com/doi/full/10.1177/1745691617713052

Loneliness and social media (review):

https://journals.sagepub.com/doi/full/10.1177/1745691617713052